Bacillus subtilis DNA replication initiation site containing fragment have been purified and will be used to study DNA replication after circularizing the fragment. We might try to amplify this fragment using proper rec minus hosts. SPPl, a B. subtilis phage uses the host polymerase III for its own DNA replication. Extensive restriction enzyme cleavage studies in concert with conventional genetic mapping and marker rescue experiments indicated involvement of 2 cistrons in the control of its DNA replication. The two gene products will be purified in order to study their role in modification of host polymerase III and initiation of DNA synthesis in vitro. The DNA fragment containing the two genes and the origin of phage DNA replication could be used as a replicon as well as a vector in future experiments. The involvement of specific restriction modification enzymes in recombination of DNA will be continued by purification and characterization of the enzymes in wild type and several Rec minus mutants. Transformation studies have been extended to mammalian cell lines using purified metaphase chromosomes. The fate of incoming DNA and its eventual participation in recombination will be analyzed by the methodology used by us for studying transformation in bacteria.